Peach Brown Rot

If you grow peaches, you’ve probably faced the frustration of fuzzy gray mold ruining your harvest. This common issue is known as Peach Brown Rot, and managing it requires a smart, season-long strategy. The good news is that with the right knowledge, you can protect your trees and enjoy a healthy crop.

This fungal disease, caused by Monilinia fructicola, attacks stone fruits like peaches, nectarines, and plums. It turns firm, ripe fruit into a mushy, rotten mess seemingly overnight. It spreads quickly, especially in warm, wet weather. Your fight against it involves cleanliness, smart watering, and well-timed treatments.

Understanding the enemy is your first step. The brown rot fungus survives winter in a few key places on your property. It hides in dried-up, shriveled fruit called “mummies” that remain on the tree or ground. It also lives in twigs and branches that have been infected, forming cankers. When spring arrives, rain and wind carry the spores to flowers, starting the cycle all over again.

What Does Brown Rot Look Like?

You’ll first notice small, circular brown spots on your developing fruit. These spots expand rapidly, and soon a dusty, tan or gray mold covers the surface. The fruit shrivels into a hard, black mummy. On blossoms, you’ll see them turn brown and wilt. Infected twigs develop sunken, gummy cankers that can girdle and kill the branch.

The Conditions It Loves

This fungus thrives under specific conditions. Knowing these helps you predict risk.

Wet Weather: Rain, heavy dew, or high humidity for 12+ hours is needed for infection.
Warm Temperatures: Ideal temps are between 68°F and 77°F (20°C-25°C).
Wounds: Insect damage, bird pecks, or cracks from growth provide easy entry points.

Your Year-Round Management Plan

Beating brown rot isn’t about one magic spray. It’s about consistent, integrated practices throughout the year.

Dormant Season (Late Winter)

This is your most important clean-up time. Your goal is to reduce the amount of fungus waiting to attack.

Remove All Mummies: Pick every single dried fruit from the tree and gather all fallen ones from the ground. Destroy them—don’t compost.
Prune Thoroughly: Cut out any dead, damaged, or diseased wood. Remove any twigs with visible cankers. Sterilize your pruners between cuts with a 10% bleach solution.
Clear Debris: Rake and remove all fallen leaves and plant material from under the tree canopy.

Pre-Bloom and Bloom (Early Spring)

Protect the flowers, as this is the first infection site. Fungicide sprays are often necessary here, especially if you’ve had brown rot before.

Apply a fungicide just as the flower buds show pink color.
A second application might be needed at full bloom if weather is wet.
Choose products labeled for brown rot on stone fruit, like those containing chlorothalonil, myclobutanil, or propiconazole.

Fruit Development (Spring to Summer)

As fruit forms, your focus shifts to protecting it and creating an unfriendly environment for the fungus.

Thin Your Fruit: Once fruit is marble-sized, thin them so they don’t touch. This improves air circulation and reduces spread.
Water at the Base: Use drip irrigation or soaker hoses. Avoid overhead watering that wets the leaves and fruit.
Monitor for Insects: Control pests like oriental fruit moths and plum curculio. Their damage opens the door for rot.

Pre-Harvest (3 Weeks Before Picking)

This is a critical spray period. The fruit is most susceptible as it sugars up and softens.

Apply a fungicide about 3 weeks before you expect to harvest.
Follow up with another application 10-14 days later if conditions are wet.
Some fungicides have a pre-harvest interval (PHI)—the number of days you must wait after spraying to pick fruit. Always read the label.

At Harvest and Post-Harvest

Careful handling prevents introducing rot to your storage area.

Harvest fruit gently to avoid bruising.
Discard any fruit with spots immediately—don’t let it touch healthy fruit.
Refrigerate harvested peaches promptly, as cold slows any latent infection.

Choosing and Using Fungicides

Fungicides are a tool, not a cure-all. Use them as part of your broader strategy. Rotate between different chemical classes (like FRAC groups) to prevent the fungus from developing resistance. Organic options include sulfur-based sprays or products containing Bacillus subtilis. These require more frequent application, especially after rain.

Always, always follow the label instructions for dosage, timing, and safety. More is not better.

Cultural Practices Are Your Foundation

These habits make everything else more effective.

Prune for Open Canopy: Annual pruning allows sunlight and air to penetrate, drying leaves and fruit quickly.
Site Selection: Plant trees in full sun with good air flow. Avoid low, frosty spots where humidity lingers.
Choose Resistant Varieties: While no peach is immune, some are less susceptible. Check with your local extension service for recommendations in your area.

Common Mistakes to Avoid

Even experienced gardeners can slip up. Here’s what to watch for.

Ignoring Mummies: Leaving last year’s fruit is inviting trouble.
Watering Overhead: Sprinklers create the perfect wet conditions for spore germination.
Poor Sanitation: Not cleaning up fallen debris allows the fungus to overwright comfortably.
Spraying Too Late: Fungicides protect against new infections; they don’t cure existing ones.

FAQ: Your Peach Brown Rot Questions Answered

Can you eat peaches with brown rot?

No, it’s best to discard infected fruit. The mold can produce mycotoxins, and the taste and texture are ruined anyway. Don’t compost them.

Does brown rot affect other plants?

Yes, the same fungus attacks other stone fruits like nectarines, apricots, plums, and cherries. It can also infect almonds and some ornamental plants.

How do you treat brown rot organically?

Organic management relies heavily on the cultural practices listed above: rigorous sanitation, pruning, and water management. Organic fungicides like sulfur or copper can offer some protection but need careful timing. Biological controls like Bacillus subtilis can also be part of a program.

Why did my peaches rot so fast after picking?

This is a classic sign of a latent infection. The fruit was infected on the tree, but the symptoms weren’t visible yet. Once picked, the rot progresses rapidly. This highlights the importance of pre-harvest sprays and cooling fruit quickly.

Can you prevent brown rot without spraying?

It is very challenging, especially in humid climates. If your tree has a history of severe infection, some spraying is usually necessary. In drier climates, perfect sanitation and cultural controls may be enough to keep it at bay.

Managing Peach Brown Rot is an ongoing commitment. It might seem like a lot of work, but the reward is baskets of healthy, beautiful peaches from your own garden. Start with a thorough winter clean-up, stay vigilant with your spring and summer practices, and you’ll significantly tip the scales in your favor. Remember, consistency is key—every season’s effort builds towards a healthier tree and a more abundant harvest.